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Abstract:

A method which directly incorporates patterning fidelity into the design
of a patterning system is provided. A production result of a target
pattern is simulated according to a set of design parameters to obtain a
simulated pattern. The target pattern is compared with the simulated
pattern to obtain a patterning fidelity, and the values of the set of
design parameters of the patterning system are adjusted according to a
target patterning fidelity to optimize the values of the set of design
parameters of the patterning system.

Claims:

1. A method which directly incorporates patterning fidelity into design
of a patterning system, comprising: providing a target pattern and a set
of exposure parameters; providing a set of design parameters; providing a
first target value range of a target patterning fidelity and a first
predetermined value of iteration number of the set of design parameters
to adjust the patterning system; simulating a production result of the
target pattern according to the set of design parameters and the set of
exposure parameters to obtain a simulated pattern; comparing the target
pattern with the simulated pattern to obtain a patterning fidelity;
determining whether the patterning fidelity is within the first target
value range or the iteration number of the set of design parameters is
adjusted to reach the first predetermined value; and when the patterning
fidelity is not within the first target value range or the iteration
number of the set of design parameters does not reach the first
predetermined value, adjusting the values of the set of design parameters
of the patterning system according to the target patterning fidelity, so
as to optimize the values of the set of design parameters of the
patterning system.

2. The method according to claim 1, wherein the patterning fidelity is a
quantification result of patterning, wherein the quantification result
includes critical dimensions, critical dimension uniformity, line edge
roughness, line width roughness or line end shortening, and the target
patterning fidelity is defined in the specifications of semiconductors.

3. The method according to claim 1 further comprising: providing a set of
initial design parameters; providing a second target value range of a set
of target focusing property parameters and a second predetermined value
of iteration number of the set of initial design parameters to adjust the
values of the set of initial design parameters; simulating focusing
properties of the patterning system according to the set of initial
design parameters to obtain values of a set of simulated focusing
property parameters; determining whether the values of the set of
simulated focusing property parameters are within the second target value
range or the iteration number of the set of initial design parameters is
adjusted to reach the second predetermined value; when the values of the
set of simulated focusing property parameters are not within the second
target value range or the iteration number of the set of initial design
parameters does not reach the second predetermined value, adjusting the
values of the set of initial design parameters according to the set of
target focusing property parameters; and when the values of the set of
simulated focusing property parameters are within the second target value
range or the iteration number of the set of initial design parameters is
adjusted to reach the second predetermined value, serving the adjusted
values of the set of initial design parameters as the initial values of
the set of design parameters for simulating the production result of the
target pattern.

4. The method according to claim 3, wherein initial values of the set of
initial design parameters are obtained by interpolating values
heuristically selected according to past experiences.

5. The method according to claim 4, wherein the simulated focusing
property parameters comprise a simulated focal point size, a simulated
depth of focus, and a simulated working distance.

6. The method according to claim 1, wherein the set of design parameters
comprise at least one or a combination of a thickness of the electrode, a
thickness of the focusing lens, a diameter of the electrode, a diameter
of the focusing lens, a voltage of the electrode, and a voltage of the
focusing lens of the patterning system.

7. The method according to claim 1, wherein the patterning system is a
particle beam direct write patterning system and the patterning system
gradually patterns a substrate of the patterning system at different time
points according to the target pattern.

8. The method according to claim 7, wherein the particle beam comprises
at least one or a combination of a photon beam, an electron beam, and an
ion beam.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of Taiwan application
serial no. 100126025, filed on Jul. 22, 2011. The entirety of the
above-mentioned patent application is hereby incorporated by reference
herein and made a part of this specification.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention generally relates to a patterning system, and more
particularly, to a method for designing a patterning system.

[0004] 2. Description of Related Art

[0005] In recent years, along with the micronization of semiconductor
devices, micro machining techniques for depicting circuit patterns by
using charged particle rays (for example, electron beam and ion beam)
have been developed in order to break the resolution limit of optical
systems.

[0006] It has become very difficult to form fine patterns through
ultraviolet lithography along with the micronization of semiconductor
devices. Thus, manufacturers in the industry have proposed and started to
develop resolutions based on lithography techniques using X-rays,
electron beams, and ion beams, etc. Previously proposed electron beam
printing lithography techniques include a projection exposure with
variable axis immersion lenses (PREVAIL), a scattering with angular
limitation in projection electron-beam lithography (SCALPEL), and a low
energy electron-beam proximity projection lithography (LEEPL).

[0007] In the PREVAIL and the SCALPEL techniques, a high-energy electron
beam with an acceleration voltage of about 100 kV is passed through part
of a mask and projected onto a photoresistor in a quarter of its original
size to produce and print a pattern. In the LEEPL technique, a low-energy
electron beam with an acceleration voltage of about 2 kV is passed
through a cavity formed on a mask to print a pattern on a photoresistor
in an equal size. Generally speaking, the higher an electron acceleration
voltage is, the less dispersed the electrons in a photoresistor are and
accordingly the less chance the electrons have to react with the
photoresistor. Thus, a highly sensitive photoresistor has to be adopted
in a lithography technique using a high-energy electron beam. Contrarily,
because the LEEPL technique adopts a low-energy electron beam, it offers
a high photoresistive sensitivity, a high resolution, and a low substrate
damage rate.

[0008] During a patterning process in a conventional lithography
technique, the focusing properties (for example, the size of the focal
point, the depth of focus, the distance between an electron-optical
system and the focal point, etc.) of the electron beam are usually
adjusted according to the specification of the pattern. However, there
may be more factors in the formation of a pattern. Thus, the patterning
result may not be satisfactory if an electron-optical system is designed
by taking only the focusing properties of an electron beam into
consideration.

SUMMARY OF THE INVENTION

[0009] Accordingly, the invention is directed to a method which directly
incorporates patterning fidelity into the design of a patterning system
to ensure that the design of the patterning system satisfies the
patterning fidelity.

[0010] The invention provides a method for designing a patterning system.
The method includes following steps. A target pattern, a set of exposure
parameters, and a set of design parameters are provided. A first target
value range of a target patterning fidelity and a first predetermined
value of iteration number of the set of design parameters to adjust the
patterning system are provided. A production result of the target pattern
is simulated according to the set of design parameters and the set of
exposure parameters to obtain a simulated pattern. The simulated pattern
is compared with the target pattern to obtain a patterning fidelity.
Whether the patterning fidelity is within the first target value range or
the iteration number of the set of design parameters is adjusted to reach
the first predetermined value is determined. If the patterning fidelity
is not within the first target value range or the iteration number of the
set of design parameters does not reach the first predetermined value,
the values of the set of design parameters of the patterning system are
adjusted according to the target patterning fidelity, so as to optimize
the values of the set of design parameters of the patterning system.

[0011] According to an embodiment of the invention, the patterning
fidelity is a quantification result of patterning, wherein the
quantification result includes critical dimensions, critical dimension
uniformity, line edge roughness, line width roughness or line end
shortening, and the target patterning fidelity is defined in the
specifications of semiconductors.

[0012] According to an embodiment of the invention, a method for obtaining
initial values of the set of design parameters includes following steps.
A set of initial design parameters is provided. A second target value
range of a set of target focusing property parameters and a second
predetermined value of iteration number of the set of initial design
parameters to adjust the values of the set of initial design parameters
are provided. Focusing properties of the patterning system are simulated
according to the set of initial design parameters to obtain values of a
set of simulated focusing property parameters. Whether the values of the
simulated focusing property parameters are within the second target value
range or the iteration number of the set of initial design parameters is
adjusted to reach the second predetermined value is determined. If the
values of the simulated focusing property parameters are not within the
second target value range or the iteration number of the set of initial
design parameters does not reach the second predetermined value, the
values of the set of initial design parameters are adjusted according to
the target focusing property parameters. If the values of the set of
simulated focusing property parameters are within the second target value
range or the iteration number of the set of initial design parameters is
adjusted to reach the second predetermined value, the adjusted values of
the set of initial design parameters are served as the initial values of
the set of design parameters for simulating the production result of the
target pattern.

[0013] According to an embodiment of the invention, initial values of the
set of initial design parameters are obtained by interpolating values
heuristically selected according to past experiences.

[0014] According to an embodiment of the invention, the simulated focusing
property parameters include a simulated focal point size, a simulated
depth of focus, and a simulated working distance.

[0015] According to an embodiment of the invention, the set of design
parameters include at least one or a combination of a thickness of the
electrode, a thickness of the focusing lens, a diameter of the electrode,
a diameter of the focusing lens, a voltage of the electrode, and a
voltage of the focusing lens of the patterning system.

[0016] According to an embodiment of the invention, the patterning system
is a particle beam direct write patterning system, and the patterning
system gradually patterns a substrate of the patterning system at
different time points according to the target pattern.

[0017] According to an embodiment of the invention, the particle beam
includes at least one or a combination of a photon beam, an electron
beam, and an ion beam.

[0018] As described above, in the invention, a patterning fidelity is
obtained by comparing a target pattern with a patterning simulation
result, and the values of a set of design parameters are adjusted
according to the target patterning fidelity, so that the design of a
patterning system can satisfy the patterning fidelity.

[0019] These and other exemplary embodiments, features, aspects, and
advantages of the invention will be described and become more apparent
from the detailed description of exemplary embodiments when read in
conjunction with accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and constitute a
part of this specification. The drawings illustrate embodiments of the
invention and, together with the description, serve to explain the
principles of the invention.

[0021]FIG. 1 is a diagram of a patterning system according to an
embodiment of the invention.

[0022]FIG. 2 is a flowchart of a method for designing a patterning system
according to an embodiment of the invention.

[0023] FIG. 3 is a flowchart of a method for obtaining initial values of a
set of design parameters according to an embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

[0024] Reference will now be made in detail to the present preferred
embodiments of the invention, examples of which are illustrated in the
accompanying drawings. Wherever possible, the same reference numbers are
used in the drawings and the description to refer to the same or like
parts.

[0025]FIG. 1 is a diagram of a patterning system according to an
embodiment of the invention. The patterning system 100 is a particle beam
direct write patterning system. The patterning system 100 includes a
charged particle source 102, a beam-limiting aperture panel 104, and a
focusing lens array 106. The charged particle source 102 generates a
particle beam. The beam-limiting aperture panel 104 reduces the emission
angle of the charged particle source 102, so as to increase the
patterning resolution. The focusing lens array 106 controls the focusing
properties of the particle beam. In the present embodiment, the focusing
lens array 106 includes three electrodes 106A-106C. The electrodes 106A
and 106C and the beam-limiting aperture panel 104 are coupled to the
ground, and the electrode 106B is coupled to an electrode voltage VC. The
focusing properties of the particle beam can be controlled by adjusting
the electrode voltage VC. It should be noted that in the present
embodiment, the focusing lens array 106 is an Einzel lens. However, the
invention is not limited thereto.

[0026]FIG. 2 is a flowchart of a method for designing a patterning system
according to an embodiment of the invention. Below, a method for
optimizing a set of design parameters of the patterning system 100 to
produce a target pattern on a substrate BS will be described by referring
to the patterning system 100 in FIG. 1, wherein the set of design
parameters comprise at least one or a combination of a thickness of the
electrode, a thickness of the focusing lens, a diameter of the electrode,
a diameter of the focusing lens, a voltage of the electrode, and a
voltage of the focusing lens of the patterning system. It should be noted
that even though the patterning system design method is described in the
present embodiment by referring to the patterning system 100 illustrated
in FIG. 1, the patterning system 100 illustrated in FIG. 1 is only an
exemplary embodiment. In actual applications, the patterning system
design method provided by the present embodiment is not limited to the
patterning system 100 illustrated in FIG. 1, and aforementioned particle
beam is not limited to an electron beam mentioned in the present
embodiment. Instead, the particle beam may also be a photon beam, an ion
beam, or a combination of electron beam, photon beam, and ion beam.

[0027] Referring to both FIG. 1 and FIG. 2, first, a target pattern and a
set of exposure parameters are provided (step S202), wherein the set of
exposure parameters include a total exposure dosage on the substrate BS,
a pixel size and a beam spot size. Then, a set of design parameters is
provided (step S204). Next, a first target value range of a target
patterning fidelity and a first predetermined value of iteration number
of the set of design parameters to adjust the patterning system are
provided (step S206), wherein the target patterning fidelity is defined
in the specifications of semiconductors. After that, a production result
of the target pattern is simulated according to the set of design
parameters and the set of exposure parameters to obtain a simulated
pattern (step S208). Herein the target pattern is simulated by assuming
that the charged particle source 102 is aligned with the focusing lenses,
there is no offset between electrodes, the focusing lenses have the same
diameter, and the charged particle source 102 and the focusing lenses are
a paraxial system.

[0028] Thereafter, the simulated pattern is compared with the target
pattern (for example, the line width of the simulated pattern is compared
with the line width of the target pattern to obtain an error deviation,
critical dimensions, a critical dimension uniformity, a line edge
roughness, a line width roughness or a line end shortening between the
line width of the simulated pattern and the line width of the target
pattern) (step S210), so as to obtain a patterning fidelity. After the
patterning fidelity is obtained, whether the patterning fidelity is
within the first target value range or the iteration number of the set of
design parameters is adjust to reach the first predetermined value is
determined (step S212). Herein determining whether the patterning
fidelity is within the first target value range may be determining
whether the error deviation, the critical dimensions, the critical
dimension uniformity, the line edge roughness, the line width roughness
or the line end shortening between the line width of the simulated
pattern and the line width of the target pattern is within a
predetermined error range. If the patterning fidelity does not reach a
first predetermined value and the iteration number of the set of design
parameter does not reach the first predetermined value, the values of the
set of design parameters of the patterning system 100 are adjusted
according to the target patterning fidelity (step S214), and step S208 is
then executed again to perform patterning simulation again according to
the adjusted values of the set of design parameters, so as to obtain a
new simulated pattern. Steps S208-S214 are repeatedly executed until the
patterning fidelity reaches the first predetermined value or the
iteration number of the set of design parameter reaches the first
predetermined value, so as to complete the optimization of the values of
the set of design parameters of the patterning system 100 (step S216).
The set of design parameters used for the final simulation is provided
for the patterning system 100.

[0029] It should be noted that the set of design parameters used for
simulating the production result of the target pattern may be obtained by
interpolating values heuristically selected according to past experiences
or through the method for obtaining initial values of the set of design
parameters illustrated in FIG. 3. As shown in FIG. 3, the method for
obtaining the initial values of the set of design parameters includes
following steps. First, a set of initial design parameters is provided
according to the specification of the target pattern (step S302), wherein
initial values of the set of initial design parameters are obtained by
interpolating values heuristically selected according to past
experiences, and the set of initial design parameters may include the
thicknesses of the electrodes 106A-106C, the diameters of the focusing
lenses in the focusing lens array 106, and the value of the electrode
voltage VC in the patterning system 100. Then, a second target value
range of a set of focusing property parameters and a second predetermined
value of iteration number to adjust the values of the set of initial
design parameters are provided (step S304). Next, the focusing properties
of the patterning system 100 are simulated according to the set of
initial design parameters to obtain values of a set of simulated focusing
property parameters (step S306), wherein the simulated focusing property
parameters include the size of a simulated focal point, a simulated depth
of focus, and a simulated working distance. Herein the simulated working
distance refers to the simulated distance between the electrodes 106C and
the substrate BS.

[0030] Similarly, the simulated focusing property parameters are simulated
results obtained by assuming that the charged particle source 102 is
aligned with the focusing lenses, there is no offset between the
electrodes, the focusing lenses have the same diameter, and the charged
particle source 102 and the focusing lenses are a paraxial system. It
should be noted that the set of initial design parameters and the
simulated focusing property parameters listed above are only exemplary
examples but are not intended to limit the scope of the invention.

[0031] Thereafter, whether the values of the simulated focusing property
parameters are within the second target value range or the iteration
number of the set of initial design parameters is adjusted to reach the
second predetermined value is determined (step S308). If the values of
simulated focusing property parameters are not within the second target
value range and the iteration number of the set of initial design
parameters does not reach the second predetermined value, the values of
the set of initial design parameters of the patterning system 100 are
adjusted according to the set of target focusing property parameters
(step S310), and step S306 is then executed again to simulate the
focusing property parameters of the patterning system 100 according to
the adjusted values of the set of initial design parameters, so as to
obtain new values of simulated focusing property parameters. If values of
the simulated focusing property parameters are within the second target
value range or the iteration number of the set of initial design
parameters is adjusted to reach the second predetermined value, the
adjusted values of the set of initial design parameters are served as the
initial values of the set of design parameters for simulating the
production result of the target pattern (step S312). Steps S306-S310 are
repeatedly executed until the values of the simulated focusing property
parameters are within the second target value range or the iteration
number of the set of initial design parameters are adjusted to reach the
second predetermined value, so as to optimize the simulated focusing
property parameters and obtain a set of design parameters for simulating
the production result of the target pattern.

[0032] As described above, in the invention, a patterning fidelity is
obtained by comparing a target pattern with a patterning simulation
result, and the values of a set of design parameters are adjusted
according to the target patterning fidelity, so that the patterning
result can be ensured to satisfy its specification before a system is
assembled and tested, and accordingly the fabrication cost of the
patterning system can be reduced.

[0033] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
invention without departing from the scope or spirit of the invention. In
view of the foregoing, it is intended that the invention cover
modifications and variations of this invention provided they fall within
the scope of the following claims and their equivalents.